1. Field of the Invention
The present invention relates to a zoom lens system used in an optical device such as digital still camera.
2. Related Background Art
A positive-negative-positive zoom lens system has conventionally been known. This positive-negative-positive zoom lens system is constituted by three lens groups of a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from an object. Upon zooming from a wide-angle end state (where the focal length is the shortest) to a telephoto end state (where the focal length is the longest), the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the first lens group moves toward the object. For focusing, the first lens group as a whole is moved along the optical axis (see, for example, Japanese Patent Publication No. 2691563).